IMPROVEMENTS RELATING TO WIND TURBINE BLADE MANUFACTURE
A method of forming a wind turbine blade shear web flange section (36) by resin transfer moulding comprises providing a mould assembly (84) comprising a mould surface (86) defining a mould cavity and arranging a plurality of elongate flange elements (46) with the mould surface in an array (80) such that the flange elements are positioned one on top of another with first and second longitudinal ends (56,60) of each flange element longitudinally offset from respective first and second longitudinal ends of a neighbouring flange element so as to form a tapered portion (58,62) at each of a first and second longitudinal end of the flange section (36). A The method further comprises injecting resin to the mould cavity and curing the array of flange elements in a resin matrix to form a cured flange section having a laminate construction.
The present invention relates generally to wind turbine blades and more specifically to a flange of a wind turbine blade shear web.
BACKGROUNDModern wind turbine blades comprise an outer shell that defines the aerodynamic contour of the blade. One or more shear webs are typically arranged inside the outer shell. The shear webs are longitudinally-extending structures comprising a panel with upper and lower flanges extending along longitudinal edges of the panel. These flanges are used to bond the shear web to opposed load-bearing spar caps which may be integrated within the shell structure, or bonded to an inner surface of the shell.
An example of a known shear web flange is described in applicant's PCT application WO2016/177375A1. The flange is substantially T-shaped in cross-section and comprises an upstand extending transversely to a base. As described in this application, the use of pre-manufactured shear web flanges simplifies the manufacturing process of a shear web because it allows relatively simple shear web tooling and moulding processes to be used, and further avoids the need for subsequent bonding of return flanges.
The T-shaped flanges described in WO2016/177375A1 are formed using a pultrusion process, in which resin-coated fibres are pulled through a T-shaped pultrusion die. The pultrusion process necessarily requires a significant proportion of the fibres to extend parallel to the length of the flanges (i.e. in the 0° direction). However, the 0° fibres in these pultruded flanges may in some cases impart an undesirably high level of longitudinal stiffness to the flanges. If the longitudinal stiffness of the flanges is too high, a proportion of the bending loads may be carried by the flanges instead of by the spar caps. It is therefore desirable to reduce or avoid the use of longitudinally oriented 0° fibres in the shear web flanges.
A shear web flange may be divided into longitudinal flange sections to accommodate blade twist resulting from the variable geometry of a wind turbine blade along its length. Dividing the shear web flange into longitudinal flange sections also assists in the transportation of components before final assembly to complete the wind turbine blade. When manufacturing a shear web, the flange sections are arranged end to end.
Opposed ends 502a, 502b of the known flange sections 500a, 500b have been chamfered transversely to their longitudinal axes A-A in order to form a sufficiently strong bond between adjacent flange sections 500a, 500b. The chamfered ends 502a, 502b define bonding surfaces 504a, 504b to which adhesive is applied before pressing the surfaces 504a, 504b together to form a bonded joint between the flange sections 500a, 500b. Chamfering the ends 502a, 502b of the flange sections 500a, 500b achieves a sufficiently strong joint between the sections 500a, 500bbut also results in a considerable wastage of material, since large portions of the flange sections 500a, 500b must be discarded when making the chamfered cuts. This material wastage adds significant cost to the overall cost of materials for the blade.
Discontinuities along the shear web flange, for example where adjacent flange sections join, can result in stress concentrations when the blade undergoes loading in use. Accordingly, it is desirable to increase the bonding area to minimize stress concentrations at the joints between adjacent flange sections. However, in the case of the prior art, a compromise must be made between material wastage and a desirable bond area which may come at the cost of increased stress concentrations at the joint.
It is against this background that the present invention has been developed.
SUMMARY OF THE INVENTIONIn a first aspect of the invention there is provided a method of forming a wind turbine blade shear web flange section by resin transfer moulding (RTM). The method comprises providing a mould assembly comprising a mould surface defining a mould cavity and arranging a plurality of elongate flange elements with the mould surface in an array such that the flange elements are positioned one on top of another with first and second longitudinal ends of each flange element longitudinally offset from respective first and second longitudinal ends of a neighbouring flange element so as to form a tapered portion at each of a first and second longitudinal end of the flange section. The method further comprises injecting resin to the mould cavity and curing the array of flange elements in a resin matrix to form a cured flange section having a laminate construction.
Resin transfer moulding (RTM) means a closed mould process in which fibrous reinforcement material is placed in a matched mould. Resin is then injected under pressure into the mould cavity which flows through the fibres to fill the mould space. The matched mould is typically in two parts that are clamped or pressed together. RTM is distinguished from vacuum bag moulding, such as vacuum assisted resin transfer moulding (VARTM) where there is no matched mould, and instead a flexible sheet is placed over dry fibrous material to form a mould cavity and once the mould cavity is sealed vacuum is applied and resin is infused into the mould cavity.
The flange elements are arranged on a first portion of the mould surface so as to form a base of the flange section, and on a second portion of the mould surface, which extends substantially away from the first portion, so as to form an upstand of the flange section extending substantially away from the base of said flange section.
The flange elements may be pre-formed with a substantially L-shaped cross section prior to arranging the flange elements with the mould surface. Preferably the flange elements comprise a fibrous material such as +/−45 degree biaxial fabric. The fibrous material may comprise less than 30% of fibres oriented in a longitudinal direction of the flange element. Preferably the fibrous material comprises 0% of fibres oriented in a longitudinal direction of the flange element.
Consecutive flange elements in the array are arranged with at least one longitudinal edge offset from a corresponding longitudinal edge of a neighbouring flange element to form an upstand which tapers with increasing distance from the base, and/or a base which tapers with increasing distance from the upstand.
The mould cavity may have a substantially T-shaped profile in cross-section. Four or more flange elements may be arranged in the array such that at least two flange elements form a first side of the flange section and at least two flange elements form a second side of the flange section resulting in a substantially T-shaped flange section.
The flange elements on the second side of the flange section are arranged such that first longitudinal ends of said flange elements are longitudinally offset from corresponding first longitudinal ends of the flange elements on the first side of the flange section.
A method of manufacturing a wind turbine blade shear web may be provided, the method comprising: arranging an elongate panel; arranging a plurality of flange sections along a longitudinal edge of the elongate panel, the flange sections being formed as set out above; integrating the plurality of flange sections and the elongate panel to form a wind turbine blade shear web. The tapered portions of longitudinally adjacent flange sections may overlap to define at least one scarf joint between said adjacent flange sections.
A brief description of
Each shear web flange 30a, 30b extends in the spanwise direction (S) and comprises longitudinal flange sections 36 (shown in
In this example, the shear web flanges 30a, 30b are substantially T-shaped in cross-section. The
T-shaped flanges 30a, 30b comprise a plurality of flange sections 36 each comprising a base 42 and an upstand 44 extending substantially away from the respective base 42 and having a substantially L-shaped cross-section. The upstand 44 of each flange section 36 is integrated with the shear web panel 28. The base 42 of each flange section 36 defines a mounting surface 45 which, by means of adhesive 40, is bonded to a spar cap 38a, 38b. The shear web 26, is therefore mounted between the opposed spar caps 38a, 38b via the mounting surface 45 defined by the base 42 of each flange section 36.
Each flange section 36 is formed of a plurality of flange elements 46 as will be described in more detail below. The flange sections 36 that form a shear web flange 30a, 30b may not necessarily all have the exact same profile. For example, it is possible to form flange sections 36 having a variety of profile shapes dependent on the prescribed location of a flange section 36 in the shear web flange 30, 30b. In the example shown in
Further to this, a chordwise C width of the flange 30a, 30b may vary along the spanwise S length of the shear web 26 to provide optimal site specific structural properties along the blade 10. The flange sections 36 can be tailored as a result of the properties of individual flange elements 46 such as width and material of an element 46 and in how the flange elements 46 are arranged with one another. Alternatively, each of the flange sections 36 may comprise a uniform width resulting in a shear web flange 30a, 30b having a uniform chordwise C width along its entire spanwise S length.
The flange elements 46 comprise a fibrous material such as +/−45° biaxial fabric in which the fibres are oriented at +/−45° to the longitudinal direction (S) of the flange element 46. In an example, the fibres are glass fibres. In preferred examples, the fibrous material comprises less than 30% of fibres oriented in the longitudinal direction (S) of the flange element 46. Preferably the fibrous material comprises 0% of fibres oriented in the longitudinal direction (S) of the flange element 46.
The shear web flange 30 formed by a plurality of the flange sections 36 shown in
The flange elements 46 are substantially L-shaped in cross-section, each flange element 46 comprising a base 52 and an upstand 54 which extends substantially away from the base 52. In the example illustrated in
The flange elements 46 are offset from one another in a longitudinal direction (S) of the flange section 36, i.e. a first longitudinal end 56 of each flange element 46 is longitudinally offset from a corresponding first longitudinal end 56 of a neighbouring flange element 46, defining a tapered portion 58 at the first longitudinal end 48 of the flange section 36. In the present example, the flange elements 46 are of equal length (L) and the longitudinal offset of the respective first ends 56 of the flange elements 46 therefore results in a similar longitudinal offset of a second longitudinal end 60 of each flange element 46 from that of a neighbouring flange element 46 defining a further tapered portion 62. A tapered portion 58, 62 is thereby formed at each of the first and second longitudinal ends 48, 50 of the flange section 36.
As shown in
Flange sections at the root end 18 and tip end 20 of the flange 30 are formed differently from the flange sections 36 described herein. The tapered portions 58, 62 of a flange section 36 are configured to form a scarf joint between longitudinally adjacent flange sections 36 in a shear web flange 30. Therefore, in a tipmost or rootmost flange section having only one other longitudinally adjacent flange section 36, a tapered portion may only be formed at one of the first or second longitudinal ends 48, 50 of said tipmost or rootmost flange section.
Longitudinal edges 68 of each flange element 46 are offset from one another in a direction T normal to the longitudinal direction B of the flange section 36. As a result of the offset between corresponding longitudinal edges 68 of each flange element 46, the upstand 44 of the flange section 36 tapers; a chordwise C thickness X of the upstand 44 decreasing as a distance Y from the flange section base 42 increases. In this example, further longitudinal edges 70 of the flange elements 46 are similarly offset from one another such that a thickness H of the flange section base 42 decreases with increasing distance Q from the upstand 44. In other examples, a flange section 36 may comprise flange elements 46 each having different widths. In this case even with an offset between longitudinal edges 68 of each flange element 46 to form a tapered upstand 44, the further longitudinal edges 70 of each flange element 46 are aligned with one another resulting in a base 42 having a constant thickness H across the chordwise C width of the flange section 36.
Although each of the flange sections 36 in the example shown in
The flange sections 36 are arranged such that longitudinal ends 48, 50 of the plurality of flange sections 36 on the first side 34a of the elongate panel 28 are longitudinally offset from the longitudinal ends 48, 50 of the plurality of flange sections 36 on the second side 34b of the elongate panel 28. Accordingly, scarf joints 72, 74 formed between longitudinally adjacent flange sections 36 on the first side 34a of the shear web 26 are longitudinally offset (i.e. in a spanwise direction) from scarf joints 72, 74 formed between longitudinally adjacent flange sections 36 arranged on the second side 34b of the shear web 26. Advantageously, in a blade 10 comprising such an arrangement of flange sections 36 there is a continuous load path between the spar caps 38a, 38b, elongate panel 28 and shear web flanges 30a, 30b along the entire length of the shear web 26. Therefore, an improved joint solution between flange sections 36 of a shear web flange 30 which reduces or completely overcomes the stress concentrations at discontinuities between longitudinally adjacent flange sections 36 is provided.
In this second example, the flange sections 36 are formed according to the description of the first example above, from a plurality of L-shaped flange elements 46 arranged on top of one another and longitudinally offset from one another such that the offset between flange elements 46 defines a tapered portion at each of the first and second longitudinal ends of the flange section. Similarly, in this example the flange elements 46 comprise a fibrous material such as +/−45° biaxial fabric. A plurality of flange sections 36 are arranged along the first side 34a of the panel 28 with tapered portions overlapped to form scarf joints between longitudinally adjacent flange sections 36.
Methods of manufacturing flange sections 36 and shear webs 26 according to various examples will now be described with reference to
The flange elements 46 are arranged in an array 80 with consecutive flange elements 46 positioned one on top another. First and second longitudinal ends 56, 60 of each flange element 46 are longitudinally offset from corresponding first and second longitudinal ends 56, 60 of flange elements 46 in the array 80 to form tapered portions 58, 62 at the first and second ends 48, 50 of the flange section 36.
Adjacent flange elements 46 in the array 80 are arranged with at least one longitudinal edge 68 offset from a corresponding longitudinal edge 68 of a neighbouring flange element 46 to form a taper in a direction normal to the longitudinal direction of the flange section 46. In the present example, two longitudinal edges 68, 70 of each flange element 46 are offset from corresponding longitudinal edges 68, 70 of neighbouring flange elements 46 which results in the tapered upstand 44 and base 42 of the flange section 36 as described above with reference to
Optionally, as shown in
The flange elements 46 are bonded together in a composite moulding process to form the flange section 36.
The flange sections 36 described above are formed by a resin transfer moulding (RTM) process according to the invention. An example of this is illustrated in
As shown in
The flange elements 46 are arranged with first and second longitudinal ends 56, 60 of each flange element 46 longitudinally offset from respective first and second longitudinal ends 56, 60 of neighbouring flange elements 46. Tapered portions 58, 62 are thereby formed at first and second longitudinal ends 48, 50 of the flange section 36. Consecutive flange elements 46 in the array 80 are arranged with at least one longitudinal edge 68 offset from a corresponding longitudinal edge 68 of a neighbouring flange element 46 to form a tapered upstand 44 and/or a tapered base 42 of the flange section 36.
The flange elements 46 may be pre-formed with a substantially L-shaped cross-section prior to arranging said elements 46 with the mould surface 86. Each of the flange elements 46 therefore comprises a base 52 and an upstand 54 extending substantially away from the base 52. When arranging pre-formed flange elements 46 with the mould surface 86 in the RTM process, the base 52 of each flange element 46 is arranged on the first portion 86a of the mould surface 86 to form the base 42 of the flange section 36. Similarly, the upstand 54 of each flange element 46 is arranged on the second portion 86b of the mould surface 86 so as to form the upstand 44 of the flange section 36.
The flange elements 46 may be pre-formed by arranging flange elements 46 on a mould surface 78 in a manner as described above with reference to
The mould cavity 88 may comprise a substantially T-shaped profile in cross-section as shown schematically in
As in other examples, the longitudinal offset between each of the flange elements 46 on each side 94a, 94b of the T-shaped flange section 36 results in the formation of a tapered portion 58, 62 at the first and second ends 48, 50 of the flange section 36 on each of the first and second sides 94a, 94b of the flange section 36 respectively. The flange elements 46 arranged to form the second side 94b of the flange section 36 are arranged such that first longitudinal ends 56 of said flange elements 46 are longitudinally offset from corresponding first longitudinal ends 56 of the flange elements 46 arranged to form the first side 94a of the flange section 36. The tapered portions 58 formed at the first end 56 on each of the first and second sides 94a, 94b of the flange section 36 are therefore similarly offset in the longitudinal direction.
Referring to
Each of the surfaces of a flange section 36 formed in an RTM process is a moulded surface which may be used as datum surface when assembling the flange sections 36 with other components of the blade 10. The RTM process can produce consistently uniform flange sections 36 at a high throughput rate resulting in a more cost effective manufacturing process. Further to this, a high volume fraction is achievable in the RTM process, wherein a higher ratio of reinforcing fibrous material to resin is possible than in many other moulding processes, resulting in increased structural properties of the flange section 36.
A plurality of flange sections 36 as described above are then arranged along a longitudinal edge 32 of the elongate panel 28 as shown in
In a further example, which is not in the scope of the invention, the flange sections 36 may be formed in-situ when arranging components to form the shear web 26 as shown in
The pre-manufactured flange sections 36 are arranged such that the tapered portions 58, 62 at the first and second longitudinal ends 48, 50 thereof overlap with the tapered portions 62, 58 of respective second and first ends 50, 48 of longitudinally adjacent flange sections 36. By arranging the flange sections 36 with the tapered portions 58, 62 of longitudinally adjacent flange sections 36 overlapping, at least one scarf joint 102 is formed between the adjacent flange sections 36 forming the wind turbine blade shear web flange 30.
As shown in
To form a substantially T-shaped shear web flange 30, arranging the plurality of flange sections 36 along a longitudinal edge 32 of the elongate panel 28 may comprise arranging a plurality of flange elements 46 having a substantially L-shaped cross section along both of the first and second sides 34a, 34b of the elongate panel 28 as shown in
Alternatively, a cured flange section 36 comprising a substantially T-shaped cross section as described in other examples above may be arranged along a longitudinal edge 32 of the elongate panel 28 to form a shear web flange 30 with a substantially T-shaped cross-section.
Further plies of fibrous material 100 may be arranged with the flange sections 36 and elongate panel 28 in some examples as shown in
Although the invention has been described throughout with reference to a shear web 26 of a wind turbine blade 10, it should also be appreciated that the arrangement of flange sections 36 and methods for manufacturing described above may be equally applicable to other structural webs in a wind turbine blade 10. For example, a trailing edge web, used in addition to a shear web 26 to provide structural support to the trailing edge 24, may be similarly constructed from flange sections 36 comprising the features as described above and following a method described above with reference to a shear web 26.
Claims
1. A method of forming a wind turbine blade shear web flange section by resin transfer moulding (RTM), the method comprising:
- providing a mould assembly comprising a mould surface defining a mould cavity;
- arranging a plurality of elongate flange elements with the mould surface in an array such that the flange elements are positioned one on top of another with first and second longitudinal ends of each flange element longitudinally offset from respective first and second longitudinal ends of a neighbouring flange element so as to form a tapered portion at each of a first and second longitudinal end of the flange section;
- injecting resin to the mould cavity; and
- curing the array of flange elements in a resin matrix to form a cured flange section having a laminate construction.
2. The method of claim 1, wherein the flange elements are arranged on a first portion of the mould surface so as to form a base of the flange section, and on a second portion of the mould surface, which extends substantially away from the first portion, so as to form an upstand of the flange section extending substantially away from the base of said flange section.
3. The method of claim 1, wherein the flange elements are pre-formed with a substantially L-shaped cross section prior to arranging the flange elements with the mould surface.
4. The method of claim 1, wherein the flange elements comprise a fibrous material such as +/−45 degree biaxial fabric.
5. The method of claim 2, wherein consecutive flange elements in the array are arranged with at least one longitudinal edge offset from a corresponding longitudinal edge of a neighbouring flange element to form an upstand which tapers with increasing distance from the base [[(42)]], and/or a base which tapers with increasing distance from the upstand.
6. The method of claim 1, wherein the mould cavity has a substantially T-shaped profile in cross-section.
7. The method of claim 6, wherein four or more flange elements are arranged in the array such that at least two flange elements form a first side of the flange section and at least two flange elements form a second side of the flange section resulting in a substantially T-shaped flange section.
8. The method of claim 7, wherein the flange elements on the second side of the flange section are arranged such that first longitudinal ends of said flange elements are longitudinally offset from corresponding first longitudinal ends of the flange elements on the first side of the flange section.
9. A method of manufacturing a wind turbine blade shear web, the method comprising:
- arranging an elongate panel;
- arranging a plurality of flange sections along a longitudinal edge of the elongate panel, the flange sections being formed according to claim 1; and
- integrating the plurality of flange sections and the elongate panel to form a wind turbine blade shear web.
10. The method according to claim 9, wherein the tapered portions of longitudinally adjacent flange sections overlap to define at least one scarf joint between said adjacent flange sections.
Type: Application
Filed: Dec 9, 2019
Publication Date: Feb 3, 2022
Patent Grant number: 11760041
Inventors: Jonathan Smith (Southampton), Robert Charles Preston (Cowes)
Application Number: 17/298,775